This disclosure relates to levels, and particularly to torpedo levels used by electricians and other tradesmen for leveling conduits, pipes, rods and construction items to ensure that such structures are plumb and level. Torpedo levels are typically made out of extruded metal that forms two spaced parallel work surfaces and a perpendicular body in which one or more holes are formed to receive the ends of spirit level vials. Because pipes, conduits, rods and other devices are made of ferrous materials, magnetic torpedo levels may adhere to these surfaces when in use.
U.S. Pat. No. 3,213,545 to Wright discloses a typical magnetic leveling device in the prior art. The leveling device disclosed in the Wright patent forms a slot along the length of one working surface in which an elongated magnet with multiple alternating poles, commonly called a “strip magnet,” is affixed. Magnetic leveling devices of this type were ubiquitous in the construction trade until the advent of readily accessible rare earth magnets. Strip magnets, however, are not particularly strong and may typically not hold the level with sufficient strength to the object it is connected to.
U.S. Pat. No. 7,520,065 to Vernola discloses a method of affixing neodymium or “rare earth” magnets to a leveling device. In this type of leveling device, circular, rare earth magnets are press-fitted into circular holes in the body of the leveling device, and rely on friction and pressure between the body of the leveling device and the magnet, and optionally an adhesive, to retain the magnets. Rare earth magnets may dislodge from the body of the magnet or shatter, typically as a result of impact when the leveling device is dropped.
U.S. Pat. No. 7,552,540 to Wu discloses a leveling device with magnets in magnet carriers that can be inserted into grooves formed in an interior portion of the body of the device. This type of leveling device allows for the use of the same body for both a magnetic and nonmagnetic version of the same level. However, because the magnets are housed away from the working surface of the leveling device, they exert less magnetic force upon the workpiece. The mechanism, as disclosed in Wu, is difficult to implement in a torpedo level, which is constructed of extruded metal, precluding the interior magnet slots.